Today's conformal coatings include glob-top organic based coatings. Such coatings include acrylics, epoxies, urethanes, parylene or silicone materials. Such conformal coatings provide limited environmental protection from moisture, dust, vibration, and provide physical protection from handling.
Today's conformal coatings are typically several mils thick. The thinnest conformal coating produced today is made of vapor-deposited parylene and is about 15 μm thick. Thick conformal coatings can be problematic. For example, during any rework of a printed circuit board, a previously applied thick conformal coating may need to be removed (e.g., by dissolution or physical abrasion). This is time consuming, expensive and difficult. Also, thick conformal coatings can undesirably impede the transfer of heat from an electrical apparatus such as a chip or circuit substrate.
Conformal coatings are also not completely foolproof. Conformal coatings are typically not applied over electrical connectors as they affect the contact resistance. For example, if a cell phone with a thick conformal coating is immersed in a body of water, there is a high probability that the phone will not work. This is because residues or contaminated liquids can form leakage pathways between the various exposed components, connectors, assemblies or surfaces not coated.
Improvements can be made to such coatings.